1. Field of the Invention
The invention relates to a device for transmitting optical signals between units that are rotatable relative to each other. Devices of this kind are also referred to as being rotary couplings or rotary joints. It is intended that a plurality of signals be transmitted simultaneously along a plurality of channels.
2. Description of the Related Art
Various transmission systems are known for transmitting optical signals between units that are rotatable relative to each other.
An optical rotary joint for a plurality of channels, having a Dove prism, is disclosed in U.S. Pat. No. 5,568,578. An arrangement with a plurality of GRIN lenses is provided for coupling light into or out of glass fibers. In this, the individual GRIN lenses are fixed onto a support to be parallel to the axis of the rotary joint. The ends of the glass fibers are retained in ferrules and are adhesively joined to the GRIN lenses via these ferrules. For exact adjustment, the individual ferrules can be moved together with the fiber ends retained therein across the plane face of the surface ground GRIN lenses.
Another kind of optical rotary joint is disclosed in WO 01/98801. This describes a micro-optical system which comprises optical and mechanical components as a one-piece part. This design permits attainment of a substantially higher packing density of the individual glass fibers. Furthermore, a laborious adjustment of individual glass fibers or ferrules relative to the lenses becomes unnecessary, because the geometry of the support is already predetermined by the monolithic fabrication process of the micro-optical system.
A disadvantage of the known prior art is that relatively strong reflections of the transmitted light occur inside the rotary joint.